An existing runaway arrest device (RAD) sensing and cutting off overcharge of a battery of an electrically driven vehicle senses whether or not the battery is overcharged using a swelling phenomenon that a battery cell is swelled when the battery is overcharged. The RAD is configured to include a switch disposed on a side surface of the battery cell, wherein the switch is physically pushed by a swelling displacement amount of the side surface of the battery cell to sense whether or not the battery is overcharged. The RAD may be configured so that the switch is connected to a relay control line controlling power of the battery in series to cut off the power supplied to the battery when the battery is overcharged or notify a battery management system (BMS) of an abnormal phenomenon through a high voltage interlock loop (HVIL) sensing a binding state of the battery, thereby cutting off the power supplied to the battery.
However, since the RAD depends on the swelling phenomenon occurring when the battery is overcharged, when considering that the swelling phenomenon of the battery cell is a phenomenon irregularly occurring according to characteristics of the battery itself, it may be difficult to accurately sense whether or not the battery is overcharged. In addition, there are problems that several situations should be considered, for example, the switch positioned on the side surface of the battery cell and the battery cell should be configured to have a constant interval therebetween, which is difficult, the possibility of a malfunction due to external impact, or the like, is present, and a space in which the switch is mounted is required on the side surface of the battery cell in order to sense the swelling of the side surface of the battery cell.
In addition, an existing current interrupt device (CID) sensing and cutting off the overcharge of the battery of the electrically driven vehicle has a configuration in which a tab part of the battery cell is cut so that the battery cell deviates from an original position using the swelling phenomenon of the battery cell when the battery is overcharged.
However, since the CID has a weak point mechanically formed intentionally in order to operate sensitively to the swelling phenomenon of the battery cell occurring when the battery is overcharged, it has a disadvantage that mechanical reliability is decreased and a disadvantage that a space in which a device is mounted is required on the side surface of the battery cell in order to sense the swelling phenomenon of the battery cell, as in the RAD.
U.S. Patent Application Publication No. 2011-0298463 has disclosed a battery state monitoring circuit and a battery device.